Various substrates having transparent conductive layers, in which transparent conductive layers are provided on transparent substrates, and various films having transparent conductive layers are used as important functional components in, for example, electronic devices that utilize a light-emitting or light-receiving function. In particular, with widespread use of mobile computing devices, there have recently been advances in touch panel technology supporting a “user-friendly” graphical user interface”. Functional members used for the devices become important. In particular, a member including two-dimensionally arranged minute transparent electrodes formed by patterning a transparent conductive layer and a member including two-dimensionally arranged minute capacitive elements formed by stacking such patterned transparent conductive layers function as switches that can detect the contact position by detecting conduction or a change in capacitance due to contact with individual transparent electrodes. Functional members including substrates and films having patterned transparent conductive layers and having functions, such as electrodes and switches, are often used as materials for touch panels which combines displays and input means in electronic equipment, such as personal digital assistants (PDAs), notebook PCs, OA equipment, medical equipment, and car-navigation systems. Furthermore, such functional members are indispensable members for slimming down and miniaturization of the above-mentioned electronic devices.
In particular, regarding the touch-panel technology, many capacitive touch panels which are attached on displays, such as liquid crystal panels and CRTs, and which detect a position touched by an observer are known (see PTL 1).
Typically, such substrates having patterned transparent conductive layers are produced by patterning transparent conductive layers by etching or laser ablation, transparent conductive layers being formed by the evaporation of a metal oxide, e.g., ITO or ATO. Hitherto, in capacitive touch panels attached to displays described above, ITO has been used as a transparent conductive film material for sensor electrodes of touch panels. Meanwhile, attempts are made to provide alternatives thereto. Furthermore, possible application processes of mass production at low cost are also studied. Examples of such processes that have been developed include methods in which conductive coating materials containing, for example, conductive particles or conductive nanowires, as a conductive substance are applied to directly form patterns; and methods in which uniform conductive coating films are formed, and then patterns are formed through various patterning steps suitable for the formed coating films. A conductive pattern-covered substrate and a method of manufacturing the same is disclosed, the method including a step of distributing conductive microfibers crossing one another without aggregating or entangling them to form conductive fiber films which electrically contact one another at their crossing portions; and a step of irradiating the conductive fiber films at their desired positions with laser light to partially break or eliminate the conductive microfibers, thereby forming conductive pattern portions (see PTL 2).
In the case where the substrates having transparent conductive layers and having electrode and switching functions are used as materials for touch panels and so forth, images on displays and the like are seen through the substrates having transparent conductive layers. Thus, irrespective of which production method described above is used, it is significantly important not to visualize formed patterns. If these patterns are recognized by a difference in optical properties between a pattern formation portion configured to, for example, electrodes and switches, and a pattern-free portion on a substrate having a transparent conductive layer, satisfactory viewability of an image on, for example, a display behind the substrate having a transparent conductive layer can be reduced.
In particular, in the case where a touch panel in which a substrate or film having a transparent conductive layer and having electrode and switch functions is arranged all over a display and which receives light incidence from a high-luminance image and the external environment, electrode and switch patterns are easily visualized by only slight differences in light transmittance, reflectance, haze, and so forth, thus causing a reduction in the viewability of an image on, for example, a display.
In particular, in the case of a transparent conductive film of a fibrous conductive substance, in which rapid progress has been made in the development of the formation of a transparent conductive film by application, as a conductive substance alternative to ITO for a transparent conductive film, since it is possible to form a conductive film by application, the production efficiency is high, advantageously reducing cost, compared with conventional transparent conductive films of ITO. In addition, the transparent conductive film advantageously has low resistance and high transmittance. However, there is a problem in which a difference in haze due to fibrous conductive substance is easily visualized.
An example of a method for preventing the visualization of a transparent conductive layer pattern of a substrate or film having a transparent conductive layer is a method in which a high-resistance coating film having similar optical properties is formed in a conductive layer-free region of the substrate. For example, a transmittance-adjusting region is formed in a non-pattern formation region in such a manner that the transmission spectrum of light passing through a pattern formation region where a transparent conductive film is formed and the transmission spectrum or reflectance of light passing through the non-pattern formation region where no transparent conductive film is formed are approximated (see PTLs 3 and 4). A solution of a synthetic resin dispersed in water, a solution of paste and ammonium chloride dispersed in water, or a solution of ferric chloride and cupric chloride dispersed in water is applied onto a predetermined portion of an upper surface of a conductive layer, so that silver in the conductive layer is converted into insulating silver chloride to form an insulating portion, instead of forming an insulating portion by removing silver, which is a conductive substance. Thereby, the difference in optical properties between a conductive portion and the insulating portion is reduced (see PTL 5).
However, in these techniques, after the transparent conductive film pattern or the transparent conductive film is formed, the transmittance-adjusting layer is separately formed in the region where no transparent conductive film is formed, or the insulating portion is formed in part of the transparent conductive film. In these cases, the production process is complicated. Furthermore, in the methods described in PTLs 3 and 4, the transmittance-adjusting region is required to be precisely formed in the portion where the transparent conductive pattern is not formed. The registration is difficult. In the case of using the chloride solution as described in PTL 5, there is a problem of the reaction of silver in the pattern formation region of the transparent conductive film inherently having satisfactory conductivity which should be maintained.
Meanwhile, a method is exemplified as follows: A conductive region similar to other conductive regions is formed in a non-formation region where no conductive pattern is originally formed, so that a narrow non-formation region, which is not easily visually recognized between other conductive regions, is formed, thereby forming an isolated pattern region electrically insulated from other conductive regions. For example, after conductive fiber films are formed using conductive microfibers, desired positions are irradiated with laser light to partially break or eliminate the conductive microfibers, thereby forming isolated conductive regions insulated from other conductive regions (see PTL 2). PTL 2 discloses a conductive pattern-covered substrate and a method of manufacturing the same, the method including a step of distributing conductive microfibers crossing one another without aggregating or entangling them to form conductive fiber films which electrically contact one another at their crossing portions; and a step of irradiating the conductive fiber films at their desired positions with laser light to partially break or eliminate the conductive microfibers, thereby forming conductive pattern portions. In this method, a non-conductive pattern portion also contains microfibers and a binder which are the same components as in the conductive pattern-covered substrate. Thus, the optical properties, such as a hue, light transmittance, and a haze value, of the conductive pattern portions and the non-conductive pattern portions are identical. No difference is visually recognized. The conductive pattern is not easily visually recognized. Such an isolated pattern region has the same optical properties as other conductive regions. Thus, no difference in optical properties is visually recognized. The non-formation region, which is a boundary between the isolated pattern region and the conductive region, is small in width. Thus, the boundary itself is not visually recognized. The isolated pattern region is a non-formation region and insulated from other conductive regions. Thus, the isolated pattern region has the same electrical function as the non-formation region.
The pattern formation of the non-formation region, which functions as an insulating portion, of the transparent conductive film is very effective when the conductive pattern is formed by a precise pattern formation method, for example, photolithography or laser processing. However, it is often difficult to form the isolated pattern region by a usual pattern formation method in such a manner that a visually unrecognizable width between the conductive region and the isolated pattern region is achieved and that both regions are reliably insulated from each other. In particular, in the case where an application step is used to form the conductive pattern, it is difficult to precisely form the foregoing non-formation region having a narrow width. For example, in the case where the conductive pattern is formed through an application step using a conductive coating material, it is impossible to form the foregoing isolated pattern region. In this method, the optical properties of the isolated pattern region are substantially equal to those of the formation region of the transparent conductive film. In addition, the method does not have the function of adjusting the optical properties. In this case, when a plurality of substrates or films having transparent conductive layers are bonded together as with the formation of a capacitive touch panel, in a portion where the formation regions of the transparent conductive films in the non-conducting pattern portions are superimposed, the optical transmittance can be markedly reduced to disadvantageously cause the pattern to be easily visually recognized, compared with, for example, a portion where the formation regions of the transparent conductive films in the conductive pattern portions are not superimposed.
For example, in the case where the foregoing method is employed for an X-Y type touch panel described in PTL 1, a transparent electrode portion formed of a conductive microfiber film of an X-axis trace of an X sensor array and a conductive microfiber film of a Y-axis trace of a Y sensor array are each irradiated with laser light to partially break or eliminate the conductive microfibers, thereby forming non-conductive portions which are electrically noncontact. In the case where non-conductive pattern portions where isolated conductive microfibers are left are superimposed, although the visual recognition of the pattern of each of the non-conductive pattern portions before superimposition is satisfactory, the hue, the light transmittance, and the haze value are clearly degraded, thereby disadvantageously degrading the image quality of a display device observed through the touch panel. The viewability is not improved but can be degraded, compared with a common method in which the conductive microfiber film is completely removed to form a non-conductive portion.
Usually, in the case where a transparent substrate or transparent film substrate having a patterned transparent conductive layer is used as a material for, for example, a touch panel, transparent conductive substrates, transparent conductive films, substrates or films having patterned transparent conductive layers are often combined and laminated before use. It is good if a pattern is not visually recognized in the overall laminate. Thus, even if a pattern of a substrate having a patterned transparent conductive layer is visually recognized, a substrate having a transparent conductive layer with a pattern that offsets the visual recognition may be stacked to prevent the conductive pattern from being visually recognized. However, a finer pattern formed requires higher precision of registration at the time of lamination.
For example, capacitive touch panels have problems with visual recognition as described below.
An X-Y type touch panel, which is often used in capacitive touch panels, includes a plurality of Y electrodes which extend in a first direction (for example, Y direction) and which are arranged in the second direction (for example, X direction) intersecting with the first direction; and a plurality of X electrodes which intersect with the Y electrodes, which extend in the second direction, and which are arranged in the first direction.
In the X-Y type touch panel, the capacitance of 1 line electrode in a state in which the panel is not in contact with a finger or the like (stationary state) consists of the interelectrode capacitance between adjacent electrodes, the intersection capacitance formed at intersections of the electrodes, the earth capacitance between the line and a display device arranged under the touch panel, and the wiring capacitance produced in wiring between a control IC and the touch panel. A change in interelectrode capacitance caused by touching the touch panel with observer's finger or the like is sensed to detect the position coordinates touched by the observer.
The capacitance other than the interelectrode capacitance is preferably lower. It is preferred that the area of the intersection of X and Y electrodes is designed as low as possible. To achieve sufficient position resolution, the distance between the electrodes is minimized as long as a short-circuit between adjacent electrodes does not occur.
The X electrodes and the Y electrodes are usually formed on different transparent insulating substrates. To achieve sufficient resolution, when the X electrodes and the Y electrodes are stacked, preferably, adjacent X and Y electrodes do not overlap, and uniform appearance is provided. Thus, in order to prevent adjacent X and Y electrodes from overlapping, gaps where no electrode is present are provided in a stack of the X electrodes and the Y electrodes.
In this case, in a pattern containing a fibrous transparent conductive substance in a transparent conductive layer, conductive pattern portions where electrode portions containing the fibrous transparent conductive substance are formed differ in hue, light transmittance, and haze value from gap portions where the electrode portion is not present. Thus, the gap portion present between two conductive pattern portions is clearly visually recognized. When the X electrodes and the Y electrodes, each extending in one direction, are orthogonally bonded together, the crossing portions of the conductive films of linking portions that connect the electrodes to each other are inevitably formed. The difference in optical properties occurs between the crossing portions and portions of the conductive pattern portions that are not crossed. In particular, the haze value of the conductive pattern portions is higher than that of the non-conductive pattern portions that do not contain microfibers because of light scattering due to the microfibers. That is, the difference in haze value occurs between the conductive pattern portions and the gap portions or between the conductive pattern portions where the crossing of the conductive films is not formed and the linking portions where the crossing occurs. For this reason, there are the problems with visual recognition in applications, such as touch panels, liquid crystal displays, and organic EL displays (see FIGS. 15, 16, and 17).